The present invention relates to a portable article strapping apparatus which stretches the thermoplastic strap, which is wound around the article to be packed, then welds the overlapped part of the thermoplastic strap together and cuts off the welded overlapped part from the thermoplastic strap at the same time.
A variety of packing machines have been developed for packing articles by strapping a thermoplastic strap over the article, then welding the overlapped part of the thermoplastic strap, and then cutting of the welded overlapped part from the thermoplastic strap. Examples are shown in U.S. Pat. No. 4,444,097, entitled "DEVICE FOR APPLYING AND TENSIONING A STRAPPING BAND AROUND A PACKAGE"; U.S. Pat. No. 4,254,703, entitled "ARTICLE STRAPPING METHOD AND APPARATUS"; U.S. Pat. No. 4,502,911, entitled "STRAPPING MACHINE". These packing apparatus are heavy and not movable when installed. U.S. Pat. No. 4,488,926 discloses a portable packing machine entitled "APPARATUS FOR SECURING A SYNTHETIC THERMOPLASTIC STRAP IN A BAND-LIKE FORM AROUND AN OBJECT", in which the overlapped part of the synthetic thermoplastic strap is welded together by a friction method. Similar welding process is employed in CYKLOP brand packing machine model CF 90/95 from German and STRAPEX brand packing machine Art. No. 361 from Swiss. According to U.S. Pat. No. 4,488,926, the welding mechanism, strap stretching mechanism and the strap clamping mechanism are driven a motor by means of the operation of a plurality of clutches and control switches. These complicated structure greatly increase the manufacturing cost of the machine. Another drawback of this structure of portable packing machine is its huge size. Because the friction head of the welding mechanism is controlled by a two-armed lever, the installation of the two-armed lever greatly increases the height of the machine, therefore the size of the machine cannot be reduced to the satisfactory extent. Furthermore, the swinging jaw for welding the thermoplastic strap and the clamping jaw for holding down the thermoplastic strap are separately controlled by two separate control levers and moved between the operative position and the non-operative position. Therefore, the operational procedure is complicated.